In recent years, various heat-stable alpha-amylase enzymes have been developed. Examples of such heat-stable alpha-amylase enzymes include those produced by Bacillus licheniformis, U.S. Pat. No. 4,519,934; by Clostridium thermoamylolyticum, U.S. Pat. No. 4,578,352; and by Clostridium thermohydrosulfuricum, U.S. Pat. No. 4,613,570. Of particular commercial interest are the alpha-amylase enzymes produced by Bacillus stearothermophilus. These are described by S. L. Pfueller and W. H. Elliott, J. Biol. Chem., 244, 48 (1969), and in U.S. Pat. Nos. 2,695,863 and 4,284,722.
Liquid Bacillus stearothermophilus alpha-amylase preparations are commercially available. Such preparations, however, often contain appreciable amounts of NaCl. The high salt concentration in the enzyme preparation is not desirable when the enzyme is used in liquid detergents and other applications because of its tendency to cause phase separation. The chloride ion is also undesirable as it can cause corrosion of metal containers and equipment. In addition, the commercial liquid alpha-amylase preparations often are dark in color and their concentrates may exhibit a tendency to form a precipitate on storage. For these reasons, the commercially-available Bacillus stearothermophilus alpha-amylase liquid preparations have not won ready acceptance by liquid detergent producers and others who need to formulate a cosmetically acceptable enzyme product.
An object of this invention is to provide a liquid enzyme concentrate containing the alpha-amylase of Bacillus stearothermophilus which has good enzyme and physical stability, which has little color and is noncorrosive.
The references to Bacillus stearothermophilus alpha-amylase cited above describe multistep procedures for preparing purified alpha-amylase enzyme preparations. However, these procedures are suitable only for small-scale preparations and would be far too expensive for the preparation of a commercial product. We have now discovered an inexpensive process which gives a stable liquid enzyme concentrate that is readily adapted to large-scale commercial production.